Dualism (philosophy of Mind) - Historical Overview - Plato and Aristotle

Plato and Aristotle

In the dialogue Phaedo, Plato formulated his famous Theory of Forms as distinct and immaterial substances of which the objects and other phenomena that we perceive in the world are nothing more than mere shadows.

Plato makes it clear, in the Phaedo, that the Forms are the universalia ante res, i.e. they are ideal universals, by which we are able to understand the world. In his allegory of the cave Plato likens the achievement of philosophical understanding to emerging into the sun from a dark cave, where only vague shadows of what lies beyond that prison are cast dimly upon the wall. Plato's forms are non-physical and non-mental. They exist nowhere in time or space, but neither do they exist in the mind, nor in the pleroma of matter; rather, matter is said to “participate” in form (μεθεξις methexis). It remained unclear however, even to Aristotle, exactly what Plato intended by that.

Aristotle argued at length against many aspects of Plato's forms, creating his own doctrine of hylomorphism wherein form and matter coexist. Ultimately however, Aristotle's aim was to perfect a theory of forms, rather than to reject it. Although Aristotle strongly rejected the independent existence Plato attributed to forms, his metaphysics do agree with Plato's a priori considerations quite often. For example, Aristotle's argues that changeless, eternal substantial form is necessarily immaterial. Because matter provides a stable substratum for a change in form, matter always has the potential to change. Thus, if given an eternity in which to do so, it will, necessarily, exercise that potential.

Part of Aristotle's psychology, the study of the soul, is his account of the ability of humans to reason and the ability of animals to perceive. In both cases, perfect copies of forms are acquired, either by direct impression of environmental forms, in the case of perception, or else by virtue of contemplation, understanding and recollection. He believed the mind can literally assume any form being contemplated or experienced, and it was unique in its ability to become a blank slate, having no essential form. As thoughts of earth are not heavy, any more than thoughts of fire are casually efficient, they provide an immaterial complement for the formless mind.